Numerous wireless devices exist for passing audio data between two locations. Many such devices are used for passing voice data, often during a conversation between one or more people. For example, mobile telephones commonly connect two speakers, while wireless headsets or earpieces connect the individual speakers wirelessly to their mobile telephones. Many such headsets or earpieces have been provided that use the Bluetooth standard.
The headset or an earpiece is designed to affix to a user's head or car and then wirelessly communicate with the user's mobile telephone when the user is making or receiving a telephone call. Such a device is synchronized to an associated mobile telephone, and then maintains a wireless connection with that mobile telephone. This frees the user's hands from having to manipulate the telephone, making it easier and safer to engage in a telephone conversation.
The headset or earpiece receives incoming wireless signals from the mobile telephone that correspond to incoming audio data received by the telephone from a remote caller. It then converts these incoming electrical signals into sound for the user to hear. Likewise, the headset gathers sound made proximate to the headset or earpiece (e.g., the user's voice), converts this sound to outgoing electrical signals, and transmits the outgoing electrical signals to the mobile telephone. In this way, a two-way conversation can be conducted by the user through the headset or earpiece by simply having it maintain a communication link with the associated mobile telephone.
However, given that these headsets and earpieces will be affixed to a user's head or ear, it is desirable to keep them as light and compact as possible. As a result, their battery power is typically comparatively low as compared to the associated mobile telephone. It is therefore desirable to limit the power used by a headset or earpiece as much as possible.
One way to limit the power consumption of a headset or earpiece is to shut the headset or earpiece off when the associated mobile telephone is not engaged in communication with a telephone network (i.e., when there is no current telephone call being processed). The mobile telephone must remain on to properly receive or make calls. But the headset or earpiece can remain off, conserving power. Since the user must take action to make a connection (either answering an incoming call or initiating an outgoing call), he or she can at this time turn on the headset or earpiece as well.
Some communication protocols, such as the Bluetooth protocol, perform this operation automatically. This means that when there is no telephone call, there is no active connection between the phone and the headset, but just a very simple and short information exchange to allow a rapid link establishment between the phone and the headset once a phone call occurs.
But once a call has been engaged, the headset or earpiece remains on and must maintain its connection with the mobile telephone. In order to do so, the headset or earpiece typically transmits and receives audio data packets (also called audio data frames) to and from the mobile telephone as a rate sufficient to maintain an acceptable quality of service for audio communication.
However, during voice communication (e.g., a telephone call), the user of the headset is typically not speaking all of the time. On average, a user will likely be speaking approximately half the time, and listening the other half. During times when the user is not speaking (e.g., when one or more other parties to the conversation are speaking, or when no one is speaking), there is no voice data that needs to be transmitted by the headset or earpiece. But the headset or earpiece will nevertheless convert and transmit the audio data picked up by the headset or earpiece (e.g., ambient noise), and send that audio data to the mobile telephone, despite the fact that it has no voice data on it.
This requires the headset or earpiece to continually transmit audio data, even when there is no audio data to send, draining battery power for such unnecessary transmissions, which can result in a significant loss of battery life.
In a typical Bluetooth transmission, for example, 90% of power is drawn by the physical layer (PHY) and the radio frequency (RF) circuits (e.g., 40 mA power consumption for RF and PHY, compared to 4 mA for base-band and media access controller). Assuming that in a typical conversation 50% of the data packets are silent (i.e., a user is listening, rather than talking), that means that approximately 45% the power is drained by the PHY and RF circuits. Taking into account that half to the PHY and MAC operations are transmitting and half are receiving, this means that during a silent period (i.e., when there is no voice activity in the transmitted audio data), 22.5% of the power loss is wasted sending unneeded audio data packets.
It would therefore be desirable to provide a way to limit the transmission of audio data from a remote device to a base device over a voice communication link when the remote device does not have any voice data to transmit.